CAS Key Lab of Bio-Medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences , No. 88, Keling Road, Suzhou New District 215163, People's Republic of China.
ACS Appl Mater Interfaces. 2014 Dec 10;6(23):20700-8. doi: 10.1021/am5071078. Epub 2014 Nov 26.
This paper reports the preparation and properties of color-switchable fluorescent carbon nanodots (C-dots). C-dots that emit dark turquoise and green-yellow fluorescence under 365 nm UV illumination were obtained from the hydrothermal decomposition of citric acid. Dark green fluorescent C-dots were obtained by conjugating prepared C-dots to form C-dot@C-dot nanoparticles. After successful conjugation of the C-dots, the fluorescence emission undergoes a blue-shift of nearly 20 nm (∼0.15 eV) under UV excitation at 370 nm. The C-dots emit goldenrod, green-yellow, and gold light under excitation at 455 nm, which shows that the prepared C-dots are color-switchable. Furthermore, conjugation of the C-dots results in enhanced, red-shifted absorption of the π-π* transition of the aromatic sp(2) domains due to the conjugated π-electron system. N incorporation in the carbon structure leads to a degree of dipoles for all the aromatic sp(2) bonds. The enhanced absorption in a wide range from 226 to 601 nm indicates extended conjugation in the C-dot@C-dot structure. The time-resolved average lifetimes for the three different types of C-dots prepared in this study are 7.10, 7.65, and 4.07 ns. The radiative rate (reduced decay lifetime) increases when the C-dots are conjugated in the C-dot@C-dot nanoparticles, leading to the enhanced fluorescence emission. The fluorescence emission of the C-dot@C-dot nanoparticles can be used in applications such as flow cytometry and cell imaging.
本文报道了可变色荧光碳纳米点（C-dots）的制备和性质。通过柠檬酸的水热分解，得到了在 365nmUV 照射下发射深绿松石色和绿黄色荧光的 C-dots。通过将制备的 C-dots 缀合形成 C-dot@C-dot 纳米颗粒，得到深绿色荧光 C-dots。在 C-dots 成功缀合后，在 370nmUV 激发下，荧光发射发生近 20nm 的蓝移（约 0.15eV）。C-dots 在 455nm 激发下发射金黄色、绿黄色和金色光，表明所制备的 C-dots 是可变色的。此外，由于共轭π电子体系，C-dots 的缀合导致芳香 sp(2)域的π-π*跃迁的吸收增强，红移。C 结构中的 N 掺入导致所有芳香 sp(2)键的偶极度。从 226nm 到 601nm 的宽范围的增强吸收表明 C-dot@C-dot 结构中的扩展共轭。本研究中制备的三种不同类型的 C-dots 的时间分辨平均寿命分别为 7.10ns、7.65ns 和 4.07ns。当 C-dots 在 C-dot@C-dot 纳米颗粒中缀合时，辐射率（降低衰减寿命）增加，导致荧光发射增强。C-dot@C-dot 纳米颗粒的荧光发射可用于流式细胞术和细胞成像等应用。
